Hold your waistline, Starbucks lovers. A grande White Chocolate Mocha from the coffee giant packs more sugar than a standard-sized Snickers bar. Loaded with 59 grams of sugar, it’s a super sweet treat indeed, one that recently brewed a sour experience for an unlucky customer.

The man, who prefers to remain anonymous, ordered the popular sugary caffeine jolt, but got a heap more than he bargained for. The drink, served at a Starbucks in a St. Augustine, Fla., came with an judgy side of snark. A barista slapped a label on the cup that read “DIABETES HERE I COME.” Yep, all caps to boot, to rub the insult in.

The snide comment, which a Starbucks source claims was only meant as a joke, was neither cute nor funny to the offended customer. To him, it was personal. Angry and upset, he wrote his own message on the insulting cup: “2 of my sisters are diabetics, so … not funny.”

The vexed customer later told Florida’s Action News Jax that the barista’s uncalled-for editorializing painfully reminded him of his sister’s struggles with type 1 diabetes. “That first word just automatically brought the picture of both sisters in my head, and I was taken aback," he told the TV news outlet. “Seeing and knowing the struggle my sisters went through by third, fourth grade, it definitely struck a nerve, and I didn’t just want to let it go.”

He doesn't want an apology. He wants to be sure this never happens to anyone else. The man received one anyway, with Starbucks issuing the following statement, which a spokesperson repeated to Entrepreneur this morning: “Starbucks strives to provide an inclusive and positive experience for our customers, and were disappointed to learn of this incident. We are working directly with the customer to apologize for his experience, and with our partners (employees) to ensure this does not happen again.”

The spokesperson for the Seattle-based global juggernaut would not say whether the employee responsible for the widely-publicized gaffe was disciplined or will be terminated, though we asked.

Veteran brand strategist and Entrepreneur contributor Melanie Spring says the employee in question should never have worked at the coffee shop in the first place. “It’s like if you’re an alcoholic or don’t believe people should drink alcohol, don’t serve it to them,” the founder and chief inspiration officer of Sisarina, a Washington, D.C.-based branding agency, tells Entrepreneur. “If this person was having a hard time offering sugary drinks they don’t believe in, they shouldn’t work there.”

Spring says the faux pas could be indicative of a larger problem at Starbucks -- specifically a potential failure to hire on-brand. “The concept of community is a huge part of Starbucks’ brand identity and in order for them to accept the community they serve, they have to accept customers for who they are in whatever ways they come in, and they should be trained in that.”

She says this incident should serve as a reminder to brands big and small everywhere about the importance of hiring the right people to represent your brand. “It’s your job to make sure you aren’t hiring the type of people who would have a problem delivering on your mission and then do something like this -- something terribly offensive -- that could damage your brand and hurt customer relationships.”

Bottom line: Don’t hire anyone who puts off signals that they don’t jive with your brand, even slightly. Listen to your gut. Pass on people whom you suspect might go rogue and tarnish your brand, whether in an isolated customer interaction or in front of the world with a derogatory tweet.

This unfortunate customer interaction -- which also casts a pall on the unhealthful nature on another of Starbucks’ most popular drinks -- should also serve as a hard lesson to food industry employees everywhere, Spring says. “If you don’t like what you’re serving customers, then quit,” she says. “If you want to take care of the world, then go work at vegan wrap place. If you’re not a counselor or a therapist, remember that it’s not your job to advise people on what they should and shouldn’t do.”

Speaking of doing jobs poorly, brand crisis management expert David Johnson agrees that Starbucks made a serious hiring mistake in this case. “Somehow this Starbucks location hired at least one person who thinks little of the customers.” Furthermore, it apparently failed to properly train the offending barista, the founder of Chicago-based Abraxas Group tells Entrepreneur.

To avoid making similar errors, and to skirt paying for them in the unforgiving and unforgetting court of public opinion, Johnson advises customer-facing business owners take several precautions. ”Provide clarity around what is and is not acceptable in customer interactions,” he says. “Provide more robust training at the store manager- and shift supervisor-level, and empower staff to report co-workers who are not living up to the company’s standards.”

Finally, he suggests going beyond the “one bad apple approach,” which he says Starbucks hid behind in this instance. To save face with the masses, should the need arise, Johnson suggests redirecting with a positive rebound message, in addition to an apology. Remind your customers that your brand values customer service above all else “...and point out that customers enjoy the right to enjoy anything you sell free of judgement.”

Most of us are already hard enough on ourselves about what we eat and drink in these increasingly health-conscious times. We don’t need the brands that we feed on -- and that feed off of us -- bagging on us, too.

Kim Lachance Shandrow

Kim Lachance Shandrow is the former West Coast editor at Entrepreneur.com. Previously, she was a commerce columnist at Los Angeles CityBeat, a news producer at MSNBC and KNBC in Los Angeles and a frequent contributo...